Multilayer optical stacks are well-known for providing a wide variety of optical properties. Such multilayer stacks may act as reflective polarizers or mirrors, reflecting light of all polarizations. They may also function as wavelength selective reflectors such as xe2x80x9ccold mirrorsxe2x80x9d that reflect visible light but transmit infrared or xe2x80x9chot mirrorsxe2x80x9d that transmit visible and reflect infrared. Examples of a wide variety of multilayer stacks that may be constructed are included in U.S. patent application Ser. No. 08/402,041 filed Mar. 10, 1995 now U.S. Pat. No. 5,882,774.
A problem with multilayer stacks as known in the art is that the stacks themselves may not have all of the physical, chemical, or optical properties desired. Some way of otherwise supplying these desirable properties would therefore be useful.
According to one embodiment of the invention a multilayer film has adhered to one or both of its major surfaces at least one additional layer selected for mechanical, chemical, or optical properties that differ from the properties of the materials of the layers of the optical stack.
According to another embodiment of the invention a multilayer film has adhered to one or both of its surfaces an additional layer that will protect the multilayer optical stack.